The field of the invention is systems for storing and managing medical images for a health care enterprise.
Medical images are acquired by a large number of different imaging modalities, including X-ray imaging, computed tomography X-ray, radioisotope emission imaging, computed emission tomography, magnetic resonance imaging and ultrasonic imaging. Current computer systems for storage, retrieval and viewing of digital medical images (referred to as Picture Archiving and Communication, or “PAC”, systems), typically have limited amounts of digital storage, a processor for storing and indexing images, and user workstations attached directly, or across a network, to the PAC systems for image display. These PAC systems are usually designed with a client-server structure. In such structures, the workstations, acting as image clients, run specific software designed for interacting with a specific PAC system, acting as an image server, in order to obtain and display images. The specific server software on the PAC system is designed to accept and respond only to the specific requests from the corresponding image-clients.
PAC systems are quite satisfactory for use throughout a single department (e.g., radiology) in a hospital, but difficulties arise when managing images from multiple modalities or different PAC systems used throughout a hospital or used throughout multiple hospitals in a large health care enterprise. A user needing access to images from multiple modalities on different PAC systems needs specific client software suited for each PAC image server.
In addition to image data, text information is also captured and stored by health care enterprises. Such information includes patient information, information regarding the image acquisition, and medical assessment information regarding a patient's medical condition based on an evaluation of the image. This textual information is captured by Radiology Information (“RIS”) systems, and like PAC systems, RIS systems are usually designed as a client-server system which requires particular client software for the work station. Thus, it is not likely that information can be exchanged between RIS systems from different manufacturers and it is even less likely that information can be exchanged between a PAC and RIS system.
There are also other information storage systems in typical health care enterprises. For example, there are specialized department systems, such as those for storing and retrieving diagnostic cardiology images, for interfacing to and reporting results from laboratory instruments, for pharmacy management, and so forth. There are also institution-scale Hospital Information (“HIS”) systems, such as those for patient financial and billing, or for patient admissions, discharge, and transfer (“ADT”).
All of these systems, like PAC and RIS systems, comprise specialized software designed for the particular application. And like PAC and RIS systems, these departmental or institution-scale information systems are not interoperable and cannot exchange data. Users typically require separate client software to interface with each of these systems.
Efforts have been made to standardize data objects handled by PAC systems to ameliorate the incompatibility problem. For example, the Digital Imaging and Communications in Medicine (“DICOM”) standard relevant to medical image distribution has been developed and promoted by the American College of Radiology/national Equipment Manufacturers Association (ACR/NEMA). DICOM aims to standardize formats for exchange of image data in PAC systems by defining a standard set of basic and composite data types along with a standard set of services involving those data types, all of which are representative of the imaging activities in a radiology department. Accordingly, a single workstation with a DICOM-conforming client can expect some success in accessing PAC systems from different manufacturers. Individual variations in the details of DICOM-conformance, however, may still defeat interoperability or data interchange in some instances.
A similar standard applicable to RIS systems is HL/7, a standard that aims to define formats for electronic data interchange in health-care environments. In particular, HL/7 defines message formats for exchange of information relating to a broad range of health care activities, including patient admission, discharges, transfers, patient queries, billing, clinical observations, and orders, and eventually patient medical records generally. Because of such broad goals, HL/7 is less of a true “plug-and-play” standard than is DICOM. In other words, two systems, although conforming to HL/7, may not be able to exchange requests and data. Therefore, a single user may still require multiple clients in order to access multiple RIS systems, even though they are all HL/7 conforming. In addition, even within one radiology department a DICOM-conforming PAC system cannot exchange service requests or data with an HL/7-conforming RIS system. The problem of using information and images from such a wide variety of sources has been addressed by systems such as that disclosed in U.S. Pat. No. 6,260,021, but such distribution systems do not address the storage of images from the wide array of devices found in a typical health care enterprise.
The storage of a large number of images and associated textual information is a complex and costly undertaking. A typical PAC system has a high speed memory which stores acquired images and makes those images available to a compatible work station. On-line memories with disk storage units using RAID technology are usually provided for such short term storage. These are relatively costly and usually they have limited storage capacity. However, RAID technology provides fast access to the images. In view of these characteristics of RAID technology, after diagnostics is performed on the image by a radiologist, the image is typically removed from the PAC system storage and archived. In the past, images were routinely archived as a film or a print out, but increasingly, images are stored in machine-readable form on magnetic tape or optical discs according to rules established by the health care enterprise. Such rules are intended, of course, to keep the images and associated textual information readily available for use while the patient is undergoing diagnosis or treatment and to archive the same to larger and less costly storage means when reasonably possible.
Consolidation in the health care industry has resulted in the formation of large, geographically widespread health care systems. These systems offer their patients high quality care and cost efficiency resulting from economies of scale. Health care systems achieve the full benefit of their economies of scale by providing an integrated network for the delivery of patient services. This means that specialized medical services, including imaging services, are leveraged across all departments and all locations. This is not achieved with current systems, however, in which images are stored on department PACs at each location and images are archived by each department on film or tape.
Advances in medical imaging technologies is compounding the problem of image distribution, storage and archiving. Medical imaging now reaches far beyond its traditional roots in Radiology. Today imaging procedures are standard diagnostic tools in Cardiology, Endoscopy, Ophthalmology, Pathology, Surgery, Dentistry and more. Unfortunately digital image management technology has not progressed much beyond its traditional roots in radiology PAC systems. In fact these systems have yet to fully master the multi-modality requirements of radiology. Sophisticated image management across all departments and specialties of the clinical practice is unknown. In addition, new digital imaging systems produce more studies per hour and more image data per study than traditional analog imaging modalities, thus further magnifying the economic and patient service issues.
Because of advances in digital storage technology film is no longer the medium of choice for archiving diagnostic images. Digital image storage is subject to lower rates of loss or damage, and studies have shown a 70 to 85% reduction in cost over film-based systems. To achieve such cost reductions, however, it is imperative that available digital data storage capacity be intelligently used. Table 1 lists example storage devices, the cost to store data in such devices based on current device purchase prices and the average retrieval time of images from the devices.
TABLE 1Cost per MBAverage RetrievalStorage Device($USD)Performance (MB/sec)RAID.06–.4050Tape.02–.0815Optical CD/DVD.001–.01 3.6
It is apparent from Table 1 that there is a tradeoff between storage cost and image retrieval time. To drive the overall storage cost down, therefore, the health care enterprise will make business decisions regarding which images will be stored in faster, higher cost devices and which will be archived to slower, low cost devices or media. For example, a radiology department may have a policy of archiving images compressed in a lossless manner stored on a RAID device to magnetic tape compressed in a lossless manner one year after the image is acquired.
A complicating factor when managing images across an entire health care enterprise is that image storage policies are not uniform. Storage policies may differ, for example, based on the imaging modality used (i.e., MRI, CT, PET, etc.), the subject of the study (i.e., head, abdomen, etc.), and the department from which the image originates (i.e., Radiology in hospital A, Radiology in hospital B, Cardiology in clinic C, etc.). The intelligent management of medical images thus requires a system which stores images acquired from many different sources throughout the enterprise, and stores the images on media and in a form that is most cost effective and in accordance with enterprise policies. The system also retrieves images from storage and delivers those images and associated textual information to workstations throughout the enterprise regardless of the particular standards or protocols that are used to acquire the images or information.